Comprehensive assessment of rice bran dietary fiber on gut microbiota composition and metabolism during in vitro fermentation

Abstract

Rice bran, a by-product of rice processing, is rich in various nutrients. As one of the main components of rice bran, dietary fiber has a variety of potential health benefits, especially its probiotic effects on gut health. This study involved the preparation and characterization of soluble rice bran dietary fibers (RB-SDF) and insoluble rice bran dietary fibers (RB-IDF), followed by an investigation into their gastrointestinal probiotic impact and principal metabolites. These results showed that rice bran dietary fiber could promote the production of short-chain fatty acids and the growth of probiotics during the fermentation in vitro. Specifically, RB-SDF significantly stimulated the growth of Bacteroides, Parabacteroides, and Acinetobacter, while RB-IDF encouraged the expansion of Tyzzerella, Pseudoflavonifractor, and Lachnospiraceae_UCG_004. Both dietary fibers could reduce the relative abundance of Escherichia_Shigella and Fusobacterium. The differential metabolites identified by untargeted metabolomics were l-pyroglutamic acid, d-(+)-tryptophan, indole-3-lactic acid, sulfolithocholic acid, 4-hydroxybenzaldehyde, indicating that different carbohydrates could significantly affect the metabolic profile of gut microbiota. Our finding indicated that rice bran dietary fiber can produce beneficial metabolites and modulate microbial ecosystems, which deserve further development for health applications.

Keywords: Gut microbiota; In vitro fermentation; Prebiotics; Rice bran; Rice bran dietary fiber; Untargeted metabolomics.